Process of producing lower alkyl-, carboxymethyl-, diethers of polyoxyalkylene glycols



Patented Sept. 29, 1953 PROCESS OF PRODUCING LOWER ALKYL-,

CARBOXYMETHYL-, DIETHERS OF POLY- OXYALKYLENE GLYCOLS Arthur B. Ash andDonald It. Jackson, Wyandotte, Mich., assignors to Wyandotte ChemicalsCorporation, Wyandottc, Mich., a corporation of Michigan No Drawing.Application June 9, 1950, Serial No. 167,254

2 Claims.

The present invention relates to lower alkyl-, carboxymethyl-, diethersof polyoxyalkylene glycols wherein the polyoxyalkylene chain has arelatively high molecular weight of 270 and above.

Lower molecular weight compounds of this type, such as the methyl-,carboxymethyl-, diether of diethylene glycol (alternatively: methyldiethylene glycol acetic acid) were synthesized by Palomaa and Siitonen,as disclosed in Berichte, vol. 63 B, p. 3117 (1930). The polyoxyalkylenegroup of such lower alkyl-, carboxymethyl-, diethers of polyoxyethyleneglycols, so far as we are aware, has not been extended to above threeethenoxy groups, corresponding to a molecular weight of about 132. SeeU. S. Patent No. 2,010,154.

The new compounds of our invention, on the other hand, correspond to thefollowing chemical formula:

R-polyoxyalkylene-CH2COO-H where R is lower alkyl, 1. e. of less than 8carbon atoms and preferably containing 1-4 carbon atoms, andpolyoxyalkylene has terminal oxygen atoms and an average molecularweight of more than 270, preferably 270-750, and is selected from thegroup consisting of polyoxyethylene and polyoxypropylene groups. Thepolyoxyethylene and polyoxypropylene groups may be present in themolecule either severally or jointly, i. e. the polyoxyalkylene portionmay be composed of oxyethylene (C2H4O) groups alone, oxypropylene(C3HsO-) groups alone, a combination of a chain of oxyethylene groupslinked to one or both terminals of a polyoxypropylene chain, and viceversa; or instead of conjugated polyoxyethylene and polyoxypropylenechains, such polyoxyalkylene portion may be a polymer of heteric ormixed ethyleneand propylene-oxides. Cf. U. S. Pat. No. 2,425,845.

These new compounds are synthesized by (1) the oxidation of a loweralkyl ether of a polyoxyalkylene glycol, in which case the terminalCH2CH2OH group of a polyoxyethylene chain is oxidized to -CH2COOI-I, andthe terminal group of a polyoxypropylene glycol chain is oxidized to-CH2COOH, involving the splitting ofi. of one CH3 radical; and (2) thecarboxymethylation of an alkali metal salt of a lower alkyl ether of apolyoxyalkylene glycol by means of a halogenated acetic acid.

The compounds of our invention are valuable intermediates in thepreparation of organic esters which in turn find use in the textile andplastics fields; are useful as detergents and especially where slightacidity is desired without corrosive attack upon metals, such as inmetal pickling baths and the removal of milkstone from dairy equipment;and are valuable as synthetic lubricants and hydraulic fluids, ascompounding ingredients in pharmaceuticals and cosmetics, and as aningredient of bufflng, burnishing, grinding and cutting compounds in themetal finishing art.

The preferred process for synthesizing our new compounds generallyinvolves the oxidation of a lower alkyl ether of a polyoxyalkyleneglycol, the total average molecular weight of whose oxyalkylene groupsis at least 2'70, in the presence oi! strong nitric acid. Suitably 2-5mols of 30-70% HNO: per mol of glycol ether are employed, and aproximately 0.05-0.5% by weight (glycol ether basis) of ammoniumvanadate as an oxidation catalyst. The oxidation reaction is conductedin an atmosphere saturated with nitrogen dioxide. Such saturation isaccomplished by either feeding in a stream of nitrogen dioxide gasduring the reaction, or by previously saturating the nitric acidsolution with such gas. The temperature of the reaction is conducted inthe range of 40-70 C. After evolution of oxides of nitrogen, excessnitric acid is removed by distilling under vacuum and flashing waterthrough the reaction mass at a temperature of 50-60 C. and a pressure ofabout 5 mm. of Hg, to remove the last traces of HNOa.

The following examples serve to illustrate our invention in greaterdetail so that those skilled in the art shall be able more readily tounderstand and practice it.

Example 1 The starting material of this example was the methyl monoetherof polyoxyethylene glycol according to the formula: CH3O(CHQC'I-I2O)MH,where (CI-IzCHzOm has a molecular weight of 728. To 200 grams (0.27 mol)of such methyl monoether of a polyoxyethylene glycol was added 121.4grams (1.35 m-ols) of 70% nitric acid in which 0.2 gram of ammoniumvanadate had been dissolved. The temperature was maintained at 50-5-55C. and a stream of nitrogen dioxide was passed over the surface of thevigorously stirred solution for 20 minutes. The balance of the nitricacid was added over a, 2 hour period. The temperature was elevated. to67 C. and a steady evolution of oxidesoi' nitrogen was observed. The

3 reaction mixture was then cooled to 55 C. and held for 2.4 hours, atwhich time the evolution of oxides of nitrogen had substantially ceased.The excess nitric acid was then removed by heating at about 50 C. at 25mm. of mercury pressure. The last traces of nitric acid were removedeffectively by reducing the pressure to about mm.

of mercury and flashing 200 ml. of water through the reaction mass -bymaintainingthe temperature between 50 and 60 C. There-was obtained 168grams of product which analyzed 80% of freemonocarboxylimacidzoflaverage molecular weight 764, and corresponding:to the formula: cnaownzonzorwcmooorr, where (CH2CH20)M'=728 minus 44(i. e. 1 mol of ethylene oxide) or 684 molecular weight.

This methyl-, carboxymethyl, diether of polyoxyethylene glycol ofmolecular weight of about 674 had the following physical properties:'

Here the starting material was a lower molecular weight methyl monoetherof polyoxyethylene glycol, viz: 'CH3O('CH2CH2O) MH, where (CH2CH20 M=317molecular Weight. This meth- A yl'monoether of polyoxye'thyl'ene glycolin the amount of 350 grams" (-1.0 mol) was added to 450- grams- (5-;0=mols) of 70% nitric acid containing 0.4 gram of ammonium vanadate andsaturated-with N02. The temperature was maintained-at 45-50 C.throughout theaddition and was then lowered-to 49-45 C. and the reactionmass was'stirred for 3 hours until-the evolution of oxides ofnitrogenhad substantially ceased. The unreacted nitricacid was removedas described in Example 1. There was obtained 354 grams of materialwhich analyzed 86% of free carboxylic acid of average molecular weight363, of the formula: CH30(CH2CH20)'M'CH2CO0H where (CH2CI-Iz'O)w=2'I3molecular weight.

Thismethy1, carboxymethyl diether-of polyoxyethylene glycol ofapproximately 273 molecular .weight hadthe following physicalproperties:

Physical appearance Transparent liquid Density; D4 11488-Refractiveindex, n5 1.4590; Pour point, F. -5 Viscosity, cps.:

25 C. 133 75 C. 14.9 pH of 5% solution 3.85 Solubility At least 5% inCC14 and water, at C.

Example 3 The starting compound in this example was n-butyl monoether ofpolyoxypropylene glycol, according to the formula:

where (CH2CH3CHO)M=806 molecular weight. Such n-butyl monoether ofpolyoxypropylene glycol was added in the amount of 109 grams (0.13 mol)to 125grams (0.99 mol) of 70% nitric acid containing 0.2 gram ofammonium vanadate and previously saturated with N02. The additionrequired 15 minutes and the temperature was held at 45-52 C. Thetemperature was .thenlowered to 40-45 C. and the reaction mass wasstirred for 7.5 hours until the evolution of Oxides of nitrogen hadsubstantially ceased. The reaction mass was worked up as described inExample 1. There was obtainediigrams of product which analyzed 89% asfree carboxylic acid of molecular weight 894 corresponding to theformula:

(CHzCHaCHOlw being equal to 748 molecular weight.

This n.butyl-, carboxymethyl-, diether of polyoxypropyl'ene glycol ofapproximately 748 molecular weight had the following physicalproperties:

Physical appearance Opaque liquid Density, D4 1.1350 Refractive index,115 1.4500 Pour point, F. +3 Viscosity, cps.:

5 C. 395 75 C. 30.8 pH 055% solution 3.48 Solubility At'least5% in CChat 30 C.', 'but insoluble in water Example 4 r The compound.oxidized'was sthe :n-butyl monoether of a polyoxyalkylene glycol of'totalaverage molecular weight 9681containing successivepolyoxypropylene and .polyoxyethylenetchains as represented by thefollowing chemical formula:

CHaCH2CI-I2CH2O(CHzCHaCHO) 1&(CH2CH2O) NH where the molecular weight of(CHzCHaCHOhr and (CH2CH2O) N are approximately 737 and 157,respectively. (Such compound was prepared by the addition .of.approximately 3.56 .mols-of ethylene oxide ton-butyl etherofpolyoxypropylene glycol 737..) A gramsample of this compound was addedto 32.5 gramsof 70% nitric acid con taining 0.2 gram-of ammonium.vanadate and saturated with NO2.. Themixturewasthen stirred at 45-47 C.for. 10.5-=hours or until the evolution of oxidesof nitrogenhadsubstantially ceased. The reactionmass.wasworkedupas described inExample 1. There was obtained 94.5 grams-of material whichanalyzed 66%-as free .carboxylic acid of: average molecular weight 982.

This n-buty1-, carboxymethyl-,.diether of polyoxypropylene 73.7 mol.wt.-polyoxyethylene. 113 mol. wt. glycol had. the followingphysicalproperties:

Physical appearance Transparent liquid Density, D4 1.0510 Refractiveindex, 15 1.4548 Pour'point, F l1 Viscosity, cps.:

25 C 389 75 C 40.6 pH of 5%-solution 4.92 Solubility At least 5% in 0014at 30 C., but insoluble in Water Example 5 A mixture of ethyleneandpropylene oxide was prepared in which the mol ratio of ethylene oxideto propylene oxide -was 2.6 to 1. This mixture was then reacted withisopropyl a1cohol in the presence iofxatsmall amount ofsodium-hydroxide. The low boiling material was distilled off and theresulting product was found on analysis to have an average molecularweight of 398.

One hundred grams of this product was then added over a 20 minute periodto 448 grams of 42 B. (67.2%) nitric acid containing 0.5 gram ofammonium vanadate as catalyst. The temperature was maintained throughoutat 42-50 C. and the reaction was stirred for a total of 4 /2 hours. Theexcess nitric acid was removed and the carboxylic acid was isolated asdescribed in Example 1. The product was the isopropyh, carboxymethylether of a mixed ethylenepropylene glycol of approximately 350 molecularweight.

It pill be apparent to those skilled in the art that our invention mayequivalently include within its scope salts of the di-ethers, i. e.,those wherein a metallic ion (which includes NH4) is substituted for theterminal hydrogen atom of the carboxymethyl group according to thefollowing exemplary formula:

R-polyoxyalkylene--CHzCOOX where: X is a metal or ammonium ion.

The appended claims are intended to include such salts within theirscope in the definition of di-ethers of polyoxyalkylene glycols.

Other modes of applying the principle of our invention may be employed,changes being made as regards to the details described, provided thefeatures stated in any of the following claims or the equivalent of suchbe employed.

We, therefore, particularly point out and distinctly claim as ourinvention:

1. The method of making mixtures of lower alkyl-, carboxymethyl-,diethers of polyoxyalkylene glycols of the type formula:

Rpolyoxyalkylene-CH2COOH 6 where: R is lower alkyl, and Polyoxyalkylenehas terminal oxygen atoms and an average molecular weight of at least286 and is selected from the group consisting of polymers ofoxyethyleneand oxypropylenegroups, taken both individually and jointly,which comprises oxidizing a mixture of lower alkyl ethers of apolyoxyalkylene glycol, the total molecular weight of whose oxyalkylenegroups is at least 330, in a reaction atmosphere that is saturated withnitrogen dioxide, such oxidation being conducted in the presence of 2-5mols of 30-70% HNOa per mol of said polyoxyalkylene glycol ether at atemperature of -70 C.

2. The method as in claim 1 wherein ammonium vanadate is present as anoxidation catalyst.

ARTHUR B. ASH. DONALD R. JACKSON.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,010,154 Hubacher Aug. 6, 1935 2,183,853 Haussmann et a1.Dec. 19, 1939 2,280,792 Bruson Apr. 28, 1942 FOREIGN PATENTS NumberCountry Date 470,181 Great Britain Aug. 3, 1937 228,415 Switzerland Jan.3, 1944 OTHER REFERENCES Palomaa et al.: Ber. Deut. Chem., vol. 633, pp.3117-20 (1930).

1. THE METHOD OF MAKING MIXTURES OF LOWER ALKYL- CARBOXYMETHYL-,DIETHERS OF POLYOXYALKYLENE GLYCOLS OF THE TYPE FORMULA: